Question

5. You have synthesized two different peptides to test for their use as drug inhibitors. However, you accidentally mixed the peptides together and need to figure out a way to separate them back apart. Using the provided table of pKa values, determine the charge (if any) on each amino acid at pH 7.0, then describe how you could chromatographically separate the two peptides at pH 7.0. (8 points) Peptide A = SMIENKRKDP Peptide B = AELRAQDKEQ

Answer 1

Peptide A = SMIENKRKDP
Length = 10
Mass = 1216.6
Isoelectric point (pI) = 9.69
Net charge AT pH 7 = +1

WS

Peptide B = AELRAQDKEQ
Length = 10
Mass = 1186.59
Isoelectric point (pI) = 4.33
Net charge at pH 7 = -1

HAN NH NH2 0 . NH2

In anion exchange chromatography, negatively charged peptides are most attracted to the resin and are leuted last.
So, peptide A will be eluted first followed by peptide B.

In cation exchange chromatography, positively charged peptides are most attracted to the resin and are leuted last.
So, peptide B will be eluted first followed by peptide A.